This invention relates to an actuator mechanism for a drum-in-hat park brake in a vehicle.
In a vehicle having four wheel disc brakes, an overall cost saving may be achieved through the use of a drum-in-hat parking brake such as disclosed in U.S. Pat. No. 5,180,037 as many of the structural components for a conventional service brake may be used in such a parking brake. A study of parking brakes revealed that less than twenty five precent of drivers effect a parking brake application on a regular basis and the use of a parking brake was even less in vehicles having an automatic transmissions. With such limited use, an initial thickness of the material of friction members for a parking brake remains essentially the same over the life of a vehicle in spite of a relative large coefficient of friction required between the friction pads and drum needed to hold a vehicle stationary in accordance with safety standards. The coefficient of friction for a friction lining for a parking brake is derived from a composition of materials mainly consisting of metal oxides, ceramic particles, carbon particles, fibers and other materials retained in a phenolic matrix. The relative limited wear is not unexpected, as a vehicle is normally stationary when a parking brake application is applied and as a result rotational frictional wear normally does not occur. However, current safety standards now require a park brake to also be capable of functioning as an emergency brake and have an ability to capable of achieving a minimum of six rolling stops from a speed of 18.6 miles per hour. In order to meet this requirement, it is not uncommon for an actuation force of approximately 100 Kg to be applied to bring brake shoes into engagement with a drum to effect such a brake application.
A drum-in-hat parking brake is commonly assembled at a first location by a first manufacturer and later installed on a vehicle at a second location by a vehicle manufacturer. At the second location, a brake cable is connection to the actuation lever in the parking brake such as disclosed in U.S. Pat. Nos. 5,174,170, 6,234,281 or U.S. patent application Ser. No. 10/171,142 filed Jun. 13, 2002. It may be difficult and time consuming for some vehicle manufacturers to install a brake cable to the lever of an actuator mechanism on an assembly line as such assembly is essentially a blind entry, it has been suggested that a stub linkage be provided with a drum-in-hat assembly the end thereof later joined to a brake cable by a crimp connection such as disclosed in U.S. Pat. No. 10/323,321 filed Dec. 18, 2002. This type connection functions in an adequate manner but lacks a positive lock between the lever and the stub linkage.
A primary object of the present invention is to provide a clip for locking a loop on a cable with a hook on a lever of an actuator in a drum-in-hat park brake.
According to this invention, an actuator mechanism for a drum-in-hat park brake in a vehicle has a housing with a first end that engages a first web of a first brake shoe and a second end that engages a second web of a second brake shoe. A lever that is pivotally retained in the housing has a first end that engages the first web and a second end with a hook thereon for receiving a loop end of a cable connected to an input member. The cable receives and transmits an input force to the loop end that causes the lever to pivot and exert an actuation force on the first and second webs to correspondingly move first and second friction members associated with the first and second brake shoes into engagement with a drum to effect a brake application. The actuator mechanism is characterized in that the lever has a projection located between the hook and the first end, a notch located on an edge of the projection that is perpendicular to a longitudinal axis of the lever, and a detent in a surface on the hook. A contiguous wire formed clip member is retained on the lever such that a first portion or segment is initially located in the notch, a second portion or segment with a lip of an arm is initially located in the detent and a third portion or segment that extends from the first portion is positioned adjacent the hook. On installation of the loop end of the cable in the actuator housing, the loop end engages the third segment and is guided toward the hook and on an installation force being applied to the cable, the loop responds by moving into the throat of the hook and into engagement with the arm. As the installation force continues to be applied to move the loop end to the bottom of the throat, the loop correspondingly acts on the arm to move the lip out of the detent and into a hole in the lever while at the same time the first segment moves out of the notch such that when the loop reaches the bottom of the throat of the hook, the lip snaps into the hole and the third portion or segment of the clip is aligned with a tip of the hook to retain the loop end in the hook.
An advantage of this invention resides in a simple wire formed clip that initially guides a loop end of a cable into a throat of a hook on a lever of an actuator for a drum-in-hat brake assembly and later locks the loop end to the hook.